Decision-making, in the interview
The 70% rule: decide before you are certain
The 70% rule says most decisions should be made once you have about 70% of the information you wish you had, because waiting for 90% usually costs more than being wrong and correcting. In an interview it is how you show judgment under uncertainty: say what you know, what you would assume, and how you would find out fast.
How does The 70% rule work?
- Say what you know and what is missing.
- Estimate whether more information would change the decision, and what waiting costs.
- Decide with explicit assumptions once you are around 70% of the way there.
- Set the signal that would make you correct course, and how quickly you would see it.
When does The 70% rule fit an interview question?
Use it whenever a hypothetical leaves information out on purpose, which is most of them. Interviewers test whether you freeze or ask for everything; stating your assumptions and committing is the strong move.
What does a strong answer with The 70% rule sound like?
Question: a retail chain wants to close 10% of its underperforming stores, which may also drive local brand awareness.
"We will never know the halo effect for sure in advance, and waiting is expensive. So I would not decide all at once: close a small set of the weakest stores first, watch online sales in those areas for a quarter, and use that to decide on the rest. That gets us to a good-enough answer quickly and keeps the rest of the decision open."
Common mistakes
- Hearing it as permission to guess: the 70% is information you have, not confidence you feel.
- Using it on one-way doors, where waiting for more evidence is worth the cost.
- Deciding without saying how you would notice you were wrong.
Where does The 70% rule come from?
Jeff Bezos wrote in his 2016 letter to Amazon shareholders that "most decisions should probably be made with somewhere around 70% of the information you wish you had", adding that being slow is likely to be expensive, and that if you are good at course correcting, being wrong may be less costly than you think.
Practice with this framework
These problems from the free GCA practice set are best answered with The 70% rule. Pick the framework that fits each one, then read the worked answer.
2 questions, one at a time
Pick a pace. The timer stops when you check an answer, and the worked method opens straight away. Nothing is saved or sent anywhere.
Keys: 1 to 4 pick an option, Enter checks and moves on.
The 70% rule: FAQ
What exactly did Bezos say about the 70% rule?
In his 2016 shareholder letter he wrote that most decisions should probably be made with somewhere around 70% of the information you wish you had, because if you wait for 90%, in most cases you are probably being slow.
Does the 70% rule apply to every decision?
No. Bezos tied it to reversible decisions, where you can correct course. For irreversible, one-way-door decisions, gathering more information first is usually worth it.
The other decision frameworks
- Reversible vs irreversibleDecide fast when a choice can be undone, and slow down for the ones that cannot (Jeff Bezos' one-way and two-way doors).
- Regret minimizationAsk which you would regret more in the long run: doing it, or not doing it (Jeff Bezos).
- CynefinFirst name the situation: clear, complicated, complex or chaotic. In a crisis, act first; in a complicated case, analyze first (Dave Snowden).
- Expected valueWeigh each outcome by its odds: the chance of a gain times its size, minus the chance of a loss times its size.
- Pre-mortemImagine the plan has already failed, list why, and build the defenses in now (Gary Klein).
- WRAPWiden your options, reality-test your assumptions, attain distance, prepare to be wrong (Chip and Dan Heath).
- 10/10/10Ask how the choice will look in 10 minutes, 10 months and 10 years (Suzy Welch).
- OODA loopObserve, orient, decide, act, and loop again faster than the situation changes (John Boyd).